Kai-Thomas Brinkmann

Triplet based online track finding in the PANDA-STT

We present a method for online track finding in the PANDA-STT which requires only knowledge of the time and straw position of the hits. Therefore, it does not depend on any additional information such as the drift-time or radius drift-time calibration which may not be present ab-initio.

Study of the New Glass and Glass Ceramic Stoichiometric and Gd3+ -loaded BaO*2SiO2 (DSB:Ce) Scintillation Material for Future Calorimetry

In the last forty years, application of crystalline materials in ionizing radiation detectors has played a crucial role in the discovery of matter properties and promoted a continuous progress in the detecting technique. Further concepts of the detectors at HEP experiments will require an unique combination of the material features, particularly in case of collider experiments. Crucially important becomes a minimal level of radiation damage effects under the electromagnetic part of ionizing radiation and energetic hadrons as well: low deterioration of the optical transmission, low level of afterglow and low level of radioluminescence due to radio-nuclides being generated due to secondary nuclear reactions in the detector material itself. A systematic study of the radiation hardness of inorganic optical and scintillation materials have been performed. We concluded that both oxide and fluoride crystals which consist of atoms with atomic number less than 60 will be reasonably survivable in the irradiation environment of future experiments at colliders. In this study we focused on the study of cheap, capable for a mass production glass (BaO*2SiO2) and DSB: Ce glass ceramics obtained from this glass. We also made this glass more heavy by admixing gadolinium oxide into the matrix. Glass with Gd3+ admixture possesses two times larger light yield than pure (BaO*2SiO2) glass and glass ceramics. Both types of the materials were produced as fibre and blocks of larger volume.

The light collection non-uniformity of strongly tapered PWO crystals and its impact on the energy resolution of the PANDA electromagnetic calorimeter in the energy region below 1 GeV

– The barrel part of the target EMC of the PANDA detector at the future FAIR facility will consist of 11 crystal geometries with a varying degree of tapering. The tapered shape introduces a focussing effect to the light collection, which in combination with the absorption of the scintillation light within the crystal causes a non-uniformity in light collection. For the most tapered crystals, light generated in the front part of the crystal is enhanced by approximately 40% compared to light generated in the rear part of the crystal. Due to the distribution of the electromagnetic shower within the crystal, this non-uniformity leads to a smearing of the energy response, resulting in a deterioration of the energy resolution. To avoid this effect, the light collection has been made uniform by de-polishing one lateral crystal side face to an average roughness Ra of 0.3 μm. Applying this method, the non-uniformity of the most tapered crystals has been decreased to a level of 5 % with a slight decrease of the light yield from the front part and a significant increase in the rear part of the crystal. This paper will discuss the observed effects of the light collection and compare the response of a 3×3 array of crystals with one de-polished side face with an identical array of completely polished crystals in the energy region below 1 GeV. In the energy region above 200 MeV a significant improvement of the energy resolution has been achieved.

Comparison of damage effects in plastic scintillators due to irradiation with γ-rays, 190 MeV and 24 GeV protons

Plastic scintillation materials play a crucial role in the construction of large area detectors in high energy physics experiments. Future detector concepts for HEP experiments, particularly at collider facilities, will require an unique combination of the material features and of affordable price. Mandatory is a minimal level of radiation damage due to the electromagnetic part of ionizing radiation and energetic hadrons as well: tolerable deterioration of the optical transmission, negligible impact on the scintillation mechanism and small contribution of radio-luminescence due to secondary reaction products in the detector material. A systematic study of the radiation hardness of inorganic optical and scintillation materials has been performed by us since several years. It resulted in the understanding of the damage effects in particular in self activated, Ce3+-doped and cross-luminescent crystalline materials. Here we report on first results for the industrially produced plastic scintillation material EJ260 (ELJEN). This plastic is a bright, fast and green light emitting scintillator with properties similar to other materials such as BC428 and NE103, respectively. Samples of a thickness of 1.25 cm were tested before and after irradiation with γ-quanta (1.2 MeV, Giessen) and protons of 190 MeV (KVI, Groningen) and 24 GeV (CERN, PS), respectively. No damage of the material properties was observed after irradiation with γ-quanta up to an absorbed dose of 1 kGy consistent with similar studies. However, the exposure to 190 MeV protons with a fluence of 5×1013p/cm2 showed a large reduction of the optical transmission and a slowing down of the scintillation kinetics. In this study we also focused on the impact of high energetic protons. We obtained evidence that light fragments of the (p,12C) reactions play a significant role in the damage of the matrix and the luminescent organic dye centers.

High-quality lead tungstate crystals available for EM-calorimetry in high-energy physics

Even at present time there is a strong interest and demand for high quality lead tungstate crystals (PbWO4, PWO) for electromagnetic (EM) calorimetry. PWO is implemented into the EM calorimeter of the CMS-ECAL detector at LHC [1] and required for the completion of the PANDA EMC [2] as well as various detector projects under discussion at Jefferson Lab or BNL in the States. The successful mass production of PWO using the Czochralski method was stopped after bankruptcy of the Bogoroditsk Technical Chemical Plant (BTCP) in Russia as the major producer so far. The Shanghai Institute of Ceramics, Chinese Academy of Science (China) was considered as an alternative producer using the modified Bridgman method. The company CRYTUR (Turnov, Czech Republic) with good experience in the development and production of different types of inorganic oxide crystals has re-started end of 2014 the development of lead tungstate for the mass production based again on the Czochralski method. An impressive progress was achieved since then. The growing technology was optimized to produce full size samples with the quality meeting the PANDA-EMC specifications for PWO-II. We will present a detailed progress report on the research program in collaboration with groups at Orsay and JLab. Full size crystals part of a pre-production run will be characterized with respect to optical performance, light yield, kinetics and radiation hardness.

Research activity with different types of scintillation materials

Nowadays there is a growing interest and demand in the development of new types of scintillation materials for experimental high energy physics. Future detector developments will focus on cheap, fast, and radiation hard materials, especially for application in collider experiments. The most recent results obtained by the Giessen group in close cooperation with colleagues from different institutes will be presented. The new start of the mass production of high quality lead tungstate crystals (PbWO4, PWO) for electromagnetic calorimetry was started by the company CRYTUR (Turnov, Czech Republic). We will present a detailed progress report on the research program of lead tungstate performed in the last two years. The latest results in the development of LuAG:Ce, YAG:Ce and LYSO:Ce inorganic fibers, grown by the micro pulling down method and cut with the heated wire technique as well as new glass ceramics material BaO*2SiO2 (DSB) doped by Ce and Gd will be presented. In addition, different samples of the organic plastic scintillator EJ-260 produced by the company Eljen Technology (Sweetwater, USA) have been characterized. The study has focused on the change of performance after irradiation with 150 MeV protons up to an integral fluence of 5-1013 protons/cm2 as well as with a strong 60Co gamma-source accumulating an integral dose of 100 Gy.

Restart of the Production of High-Quality PbWO 4 Crystals for Calorimetry Applications

Even presently there is a strong interest and demand for high-quality lead tungstate crystals (PbWO4, PWO) for electromagnetic (EM) calorimetry. PWO is implemented into the EM calorimeter of the CMS-ECAL detector at LHC [1] and is required for the completion of the PANDA EMC [2] as well as various detector projects under discussion at Jefferson Lab or BNL in the United States. The mass production of PWO using the Czochralski method had to be stopped after bankruptcy of the Bogoroditsk Technical Chemical Plant (BTCP) in Russia as the major former producer. The company SICCAS (China) was initially considered as an alternative producer but using the modified Bridgman method. The company CRYTUR (Czech Republic) with good experience in the production of different types of inorganic oxide crystals has re-started end of 2014 the development of PWO for the mass production based on the Czochralski method. The growing technology was optimized to reach a quality meeting the PANDA-EMC specifications for PWO-II. We present a detailed progress report on full size crystals part of the pre-production with respect to the optical performance, light yield, kinetics and radiation hardness.

Integration of the PANDA Micro Vertex Detector strip barrel staves

PANDA is a key experiment of the future FAIR facility and the Micro Vertex Detector (MVD) is the innermost part of its tracking system, designed to identify primary and secondary vertices. It will be composed of four concentric barrels and six forward disks, instrumented with silicon hybrid pixel detectors and double-sided microstrip detectors. The layout of the two strip barrels of the PANDA MVD foresees square and rectangular sensors, arranged in linear staves. The compact layout of the detector poses significant challenges on its integration. The staves consist of a carbon fiber support structure with an embedded cooling system. A complete stave has been used to perform a test of the cooling system, using resistors to simulate the power dissipation of the chips. A multilayer flexible bus will be used to connect the readout chips to the sensor, as well as to provide the interconnection between the various chips and to distribute the power supply to the chips and to the sensors. Different prototypes have been designed to explore the technology possibilities and to optimize the stave geometry.

Study of the glass and glass ceramic stoichiometric and Gd 3+ heavy loaded BaO∗2SiO 2 :Ce (DSB:Ce) scintillation materials for calorimetry application

Application of crystalline materials in ionizing radiation detectors has played a crucial role in the discovery of properties of matter. Future detector concepts at HEP experiments will require a tolerable level of radiation damage in particular caused by energetic hadrons: minor deterioration of the optical transmission, low level of afterglow and radio-luminescence. From systematic studies of the radiation hardness of inorganic optical and scintillation materials we concluded that both oxide and fluoride crystals composed of atoms with atomic numbers below 60 should be reasonably survivable. In this study we focuse on cheap glass (BaO*2SiO2) and (DSB: Ce) glass ceramics capable for a mass production. Loading this glass by admixing gadolinium oxide (Gd3+) provides a two times larger light yield. Both type of the materials can be produced in fiber and bulk geometry.